1. Field of the Invention
This invention relates in general to an exhaust system for an engine employed in water craft which is propelled by water jets and, in more particular, to the construction of such a system with rigidity and vibration proofing.
2. Description of the Prior Art
Various types of water craft engines which propels the craft by a jet of water streaming at high velocity from the rear of the engine. In those water craft, the engine, the water jet propulsion system, the air intake device and the exhaust system are put together in a compartment of rather limited space.
FIG. 5 illustrates the typical structure of a representative water craft engine in the prior art such as disclosed in laid-open Japanese utility model application No. 57-32249. The construction shown is a compromise between the positional relationship of the exhaust system to the engine and particularly its output shaft, the required incorporation of a diffuser, muffler and steam separator, and the balance of weight of the entire equipment.
Referring to the same drawing, the engine 1 has its output shaft 2 connected to the water jet propulsion system, not shown, on the opposite side to the exhaust system, which in turn comprises the exhaust manifold 3, exhaust pipe 4, diffuser 5, muffler 6, steam separator 7, and tail pipe 8, all connected in sequence. The exhaust system is structured such that the exhaust gas from the engine 1, after leaving the exhaust manifold 3, is conducted to turn sharply by the vertically supported exhaust pipe 4 and enter the diffuser 5 following the opposite direction to its initial flow.
In the engine compartments of those water craft, the engines, together with their exhaust systems, are generally secured in position to the floor and hull walls, with the intermediacy of elastic vibration-proof pads or mats to prevent transmission of the engine vibrations to the craft body.
However, in the past, complicated work with considerable difficulties have had to be involved in disposing the engine and its associated devices within their usually narrow compartment in such a layout that insure their normal function. Moreover, the narrowness of the space in itself have impeded securing them in positions to the compartment floor or wall.
For example, since the entire exhaust setup leading to the tail pipe 8 is connected to the engine 1 through the exhaust manifold 3 alone, the rest of the system between them including the exhaust pipe 4, diffuser 5, muffler 6, and steam separator 7 have to be rigidly secured in positions in the compartment to prevent transmission of engine vibrations to the other sections of the water craft. Furthermore, they must be connected to one another without looseness in the joints to prevent leakage of exhaust gases. In addition, since the water craft is operated in the waters, these devices must be housed in watertight condition. These requirements have demanded complicated work and, in an extreme case, have barely been met with great difficulties.
Moreover, since an exhaust system in operation emits very high temperatures, special provision has to be made to secure it in position. This has posed some difficulty with those prior art exhaust systems.